1. Field of the Invention
The present invention relates generally to industrial belts, particularly belts for use in papermaking machines, as well as to a method of making a seam and on-machine joining of the opposite ends of a non-endless belt at the seam, the seam thus created resulting in minimal sheet marking during use.
2. Discussion of Background Information
Industrial belt products, as well as methods of installation thereof, have long been limited by a failure to have available, particularly in the field of papermaking machinery, a successful and practical way to join the opposite ends of a belt during installation of the belt while on the machine.
Prior art attempts to devise products and methods for joining the ends of non-endless belts, while on the machine, are inspired by certain advantages inherent in same, such as that of reducing downtime for the machine. Despite such attempts, however, a successful, practical, belt structure and method of installation thereof have yet to appear in the marketplace.
Belts used in papermaking machines can be made as a conventional woven fabric or have a nonwoven structure, which structure can be at least partially encapsulated in a polymer matrix.
Woven fabrics for endless belts for papermaking machines can be manufactured by one of two basic weaving techniques. In the first technique, fabrics are flat woven by a flat weaving process, with their ends being joined to form an endless belt by any one of a number of well-known joining methods, such as dismantling and reweaving the ends together (commonly known as splicing), or sewing on a pin-seamable flap or a special foldback on each end, then reweaving these into pin-seamable loops. A number of auto-joining machines are available which, for certain fabrics, may be used to automate at least part of the joining process. In a flat woven papermaker's fabric, the warp yarns extend in the machine direction (MD) and the filling yarns extend in the cross machine direction (CD). In the second basic weaving technique, fabrics are woven directly in the form of a continuous belt with an endless weaving process. In the endless weaving process, the warp yarns extend in the cross machine direction and the filling yarns extend in the machine direction. Both of these weaving methods for endless belts in the art of papermaking machinery are well-known.
A papermaking belt having a nonwoven structure is disclosed in the patent document GB 2346387 (Jeffrey et al.). More particularly, GB '387 discloses a plurality of embodiments of a transfer fabric for use in papermaking machines and, more particularly, in a tissue making machine. In one particular embodiment, the fabric has a nonwoven internal reinforcing structure that includes a spiral link fabric having interdigitated spiral loops providing machine direction (MD) extending members and cross machine-direction (CD) yarns providing pintles or binding yarns which join the spirals together. The fabric Is fully impregnated with a polymer, such as polyurethane, which covers both faces of the fabric. The yarns forming both the spirals and the binding yarns can be made of a polyester, such as PET, for example. The transfer fabric is disclosed as having the following exemplary dimensions: 3-7 millimeters thick, 1-50 meters long, and up to 5 meters wide. Further, the fabric is disclosed as having a flexibility sufficient to allow for high roll wrap angles and capable of withstanding loads up to 600 pli.
Further, GB '387 discloses that the fabric can be either endless or provided with a seam, such as a seam disclosed in EP 0518494 (Buchanan et al.). If the fabric is provided with a seam, it is disclosed that such seam must have the ability to pass through a soft or hard calender nip without marking the web or disturbing the dynamics of the nip.
The referenced document EP '494 is based upon an earlier disclosure in EP 0399674 (Sayers et al.) and family member U.S. Pat. No. 5,169,570. The invention of EP '674 and US '570 relates to the joining together of opposite ends of an industrial fabric at a seam for forming an endless belt, particularly a belt for use in papermaking machines. Disclosed therein are prior attempts to provide a belt seam from seam-forming elements at the ends of a papermakers' fabric, whereby the ends are securely and uniformly joined in such manner that the permeability in the area of the seam is not materially different from that of the body of the fabric. More specifically, the invention of EP '674 and US '570 is the provision of loops or loop-like structures at a fabric end, either a woven construction or otherwise, for cooperation with a complementary formation at the opposite end of the fabric, through which loops or loop-like structures pintle wires are received.
The invention of EP '674 and US '570, although formed with loops or loop-like end structures, provides no intercogitation of the opposing elements. They merely act to present the loops/loop-like end structures in a width-wise orientation for simplifying the seaming.
The aforementioned EP '494 and family member U.S. Pat. No. 5,419,017 disclose an alternative to the invention of EP '674 and US '570, whereby an external temporary bridge is used to hook over the tops of the opposite ends of a belt which are joined by interdigitated loops engaged with a pintle wire to form the hinged seam. For securing the bridge to the ends of the belt, each end of the bridge is provided with a plurality of pegs, the pegs being complementary with apertures provided in the ends of the belt. After the two ends of the belt are seamed together, the bridge is removed.
The document WO 93/17161 (Lidar) discloses a seam for a textile belt in which joining eyelets extend from the edges of the respective ends of the belt, i.e., beyond the ends of the polymer coating of the belt, so that a flap is required to be inserted over the area of the joining eyelets to prevent marking of the sheet. The seaming technique disclosed is time-consuming and awkward and not suitable for commercialization. Further, particularly in view of the need for the seam-covering flap, it is not suitable for a rigid, or substantially rigid, fully-encased belt.
To limit sheet marking, the document EP 06958827 (Miller et al.), and family members U.S. Pat. Nos. 5,601,877 and 5,789,052, disclose a construction similar to that of WO '161, whereby an encapsulating material is added in the seam area on the reverse side of the belt fabric. Despite the improvement, the resulting belt is fundamentally a belt having a one-sided coating with a relatively flexible characteristic, in contrast to a belt, e.g., which is a rigid, or substantially rigid, fully-encased belt.
More recently, the document EP 1241378 (Takeuchi et al.) discloses the insertion of a respective independent seam element into each of the edges of the cut fabric of the belt. The use of such elements increase costs, adds a layer of complexity to the structure of the belt, and adds time-consuming steps to the, seaming of the belt, thereby risking increased downtime for installation and repairs of the affected-machinery.
An approach similar to that of EP '378 is disclosed in the document EP 1357224 (Best), and in family member U.S. Pat. No. 7,005,041, whereby “insertion connections” are used to connect coupling elements to the MD yarns. As with the EP '378 concept, that of EP '224 relies upon elements that are additional to the initial belt structure which elements increase costs, adds complexity and time-consuming steps to the seaming of the belt.
The document WO 2004/016969 (Levine) and family member US 2004/0033856 disclose an industrial belt, such as for used in a bowling alley pinspotter machine. The belt includes spiral links, which are overlapped in the machine direction, and pintles which extend through the overlapping portions of the internal spaces of the links to join the links to form a continuous material. The spiral links can be made of metal or polymer, such as polyester and polyamide, which are coated with a material having a high elasticity/impact resistance, such as a silicone rubber elastomer, preferably keeping the belt relatively thin and flexible to provide easier maneuverability when the belt is removed by a technician. In this regard, the coating is preferred to extend beyond the top surface of the spiral links by 0.010-0.250 inches or more. A surface of the coating is cut and then springs back to expose a sufficient amount of the spiral links on both sides of the seam to allow refitting onto the machine using an appropriate pintle wire. The seam thus made would not be satisfactory for certain applications, such as for papermaking machinery, since there would be a significant CD wide gap and sheet marking would result.
Despite the disclosures of the aforementioned patent documents, the need remains, particularly in the field of papermaking machinery, for a non-endless belt which is on-the-machine seamable, providing an easier and less time-consuming installation, and one which results in minimal sheet marking during use.